A mass mailing system generally comprises a mail inserting machine and a mail stacking machine. The mail inserting machine includes an envelope feeder and an enclosure document supply section. The envelope feeder is used to feed envelopes, one at a time, to an envelope insertion station. In the enclosure document supply section, a plurality of enclosure feeders is used to release enclosure documents to a chassis. The released documents are then gathered, collated and pushed by a plurality of pusher fingers to the envelope insertion station for insertion. Mail inserting machines are known in the art. For example, Roetter et al. (U.S. Pat. No. 4,169,341) discloses a mail inserting machine wherein documents are released onto a continuous conveyor mechanism to be collected and collated in a continuous matter. After the enclosure documents are inserted into the envelopes, the filled envelopes are typically transported to another piece of equipment that seals the envelopes and affixes postage or prints a postage indicium on each envelope.
The filled envelopes are typically collected and loaded by an operator into mail trays or other forms of storage. This step in the mass mailing process has been found to be a “bottleneck”. One way to assist the operator in eliminating the bottleneck is to use an envelope stacking machine to automatically collect the filled envelopes into a stack so that the operator can remove the filled envelopes in stacks. One of the commonly used envelope stackers is an on-edge stacking apparatus. For example, Keane et al. (U.S. Pat. No. 6,398,204) discloses a mail stacking machine where a belt turn-up unit is used to turn the filled envelope from a horizontally facing direction to a vertical or “on-edge” position. The vertically oriented envelope is driven by a segmented roller into the bottom of a vertical stack. Kulpa (U.S. Pat. No. 4,524,965) discloses an envelope stacking machine where a rotary displacement device is used to supply a resisting force to a stacker paddle. Belec et al (U.S. Pat. No. 5,429,249) discloses an on-line sorter, which comprises a plurality of on-edge stackers to collect the sorted mailpieces.
A typical stacking machine 1, as shown in FIG. 1, comprises a mailpiece input device 30, an incoming mailpiece moving device 40 and a stacking section 50. As shown in FIG. 1, the stacking section 50 has a stacking deck 52 to support a stack of mailpieces 20. An incoming mailpiece 10, which enters the stack section 50 from the input device 30 along a direction 310, is driven by the moving device 40 into the bottom of the stack 20. As more mailpieces 10 are added to the bottom the stack 20, the stack 20 expands or grows toward the downstream end of the stacking section 50. As the stack 20 expands, the pressure on the incoming envelope 10 increases. In order to relieve the stack pressure, a continuous conveyor belt 54 moving along a direction 320 is used to space out the stacked mailpieces, thereby making room for the next incoming mailpiece 10 to join the stack 20. At the same time, a paddle 60 is used to support the stack 20, preventing the top mailpieces of the stack 20 from falling toward the downstream end. The paddle 60 is linked to a bearing collar 70 by a handle 62. The collar 70 is movably mounted over a shaft or support rod 72 for movement. The support rod 72, which is substantially parallel to the moving direction 320, is fixedly mounted on rod mounts 74 and 76. The support rod 72, as shown in FIGS. 1 and 2, is positioned above the deck 52. As such, the support rod 72 hinders the free access needed to “sweep” or remove the stacked mail from the conveyor belt 54.
When the stacking machine 1 is used in conjunction with other equipment, such as a mail inserter, for a large-scaled mail operation, it is desirable that the stacked mail can be removed from both lateral sides of the stacking section 50. Thus, it is desirable and advantageous to provide a stacking machine wherein the mail stack 20 can be swept from either side of the stacking section.
A stacker paddle for on-edge mail stackers has traditionally been designed as a slidable member attached to a bearing or guiding journal element that is slidably fastened to a support rod or rail. The paddle is typically designed to be raised for mail sweeping and to be lowered onto the stacking deck afterward. As the paddle slices into the stack of remaining mailpieces, it tends to cause damage to the mailpieces on the stacking section. Thus, it is also desirable and advantageous to provide a stacker paddle that minimizes the damage to the stacked mail when the stacker paddle is dropped into the stack from its raised position.